For example, Japanese Unexamined Patent Application, Publication No. 1996-196950 (Patent Literature 1), or WO01/02099 (Patent Literature 2) disclose a coating material nozzle of a spray gun, which is formed with, for example, four grooves equiangularly disposed on a periphery of a coating material ejection opening of a coating material nozzle. Each groove is formed to have a cross section of, for example, a V shape, and increases in depth toward a tip of the coating material nozzle.
When the coating material is ejected from the coating material ejection opening of the coating material nozzle, compressed air is introduced to the grooves from a gun main body. The grooves are designed such that the compressed air increases in gas-liquid contact area while passing through the grooves, and then mixes with the ejected coating material by collision. As a result thereof, the compressed air, even if it were in a state of air flow under a low pressure, can be effectively atomized toward a central portion of the ejected coating material.
Furthermore, Japanese Unexamined Patent Application, Publication No. 1996-196950 (Patent Literature 1), and WO01/02099 (Patent Literature 2) disclose an air cap attached to the gun main body disposed around a coating material nozzle of a spray gun. The air cap is formed with a pair of side air holes facing toward each other to have a coating material ejection opening of the coating material nozzle sandwiched therebetween. The compressed air introduced from the gun main body is ejected through the side air holes so that the compressed air intersects with the coating material ejected from the coating material ejection opening. As a result thereof, the coating material ejected from the coating material nozzle can be sprayed in an elliptical spray pattern.